People with connections to the internet may now receive many useful services, such as maps, comparison shopping information, e-mail, search results, business software applications, and financial and blogging information. Often, such information may be obtained for free—such as with the various services offered by Google. But providing such services costs a lot of money. As a result, the content that is delivered to users of such internet services is often accompanied by advertising in various forms, to offset the cost of providing the content.
Advertisers can pay simply to have their promotional materials displayed, or they can track reactions to advertisements and pay according to that reaction. For example, advertisers may have their advertisements displayed for free, and may be charged only if a user clicks on a hyperlink in an ad—a so-called “pay-per-click” system. Advertisers may also be permitted to select an amount they are willing to pay for each click so as to improve the position of their advertisements relative to advertisements of other advertisers. The position of an advertisement, such as when it is displayed next to search results, may be a function of such a bid and the suitability of the ad, such as may be measured by the frequency with which users click on the advertisement. In this manner, advertisements that are not of interest to users will sink in the rankings, while those on which users click a lot will rise—even if the latter advertisements involve lower bid prices than do the former. The popular Google AdWords program uses such an approach.